Factors influencing chloride transport in concrete structures exposed to marine environments

Abstract

Abstract The present study concerns a literature review regarding chloride transport in terms of the diffusion coefficient ( D ) and surface chloride content ( C S ) in concrete structures exposed to a marine environment. In addition, a refined model is proposed for D and C S for time-dependent chloride transport. It is found that both D and C S are time-dependent: D decreases and C S increases with time, due to further cement hydration development. D and C S are significantly influenced by concrete mix proportion, air void content in concrete, curing methods, degree of exposure to seawater and climate. Blended cement concretes are beneficial in decreasing D , but increase C S , presumably due to a refinement of the concrete pore structures and chloride binding. An increase in the air void content in concrete increases D , but decreases C S . The C S depends on curing methods such as water, membrane and aeration. The degree of exposure to seawater does not have a clear relationship with C S : higher exposure levels did not result in a higher level of C S . Exposure in tropical areas results in higher C S in concrete jetty structures with a similar level of D , mainly due to an increased temperature and concentration of salinity. Based on these findings, a refined model for C S was proposed to provide more realistic prediction of the build-up of chlorides by chloride transport in concrete structures exposed to marine environments.